1. Field of the Invention
The invention relates generally to electric control equipment and more particularly to electrical control equipment requiring protective fuses.
2. Description of the Prior Art
In commercial amd industrial installations, electrical apparatus such as pumps, motors, fans and other equipment is controlled by contactors or relays mounted or enclosed in operating panels. The contactors and relays in turn are manually or automatically operated by control circuits. Safety considerations dictate that this control circuitry be protected by fuses whenever it leaves the enclosure in which the contactor or relay is situated. In addition, it is sometimes desirable to protect the control circuitry by fuses even when the circuitry does not leave the relay or contactor enclosure.
Previously, fuses for the control circuitry of relays and contactors have been mounted upon channels similar to terminal strips. Alternatively, the fuses have been mounted upon the contactor or relay panels. Both of these methods, however, require additional panel space and in many installations such space is at a premium. It may then be necessary to enlarge enclosures or install additional enclosures, thereby increasing the cost of the installation.
Often it is not known until late in the installation process whether fusing will be required for the control circuitry. Using prior methods, it was often extremely inconvenient to add such fusing to the installation.
It is desirable to provide an electric control device to which fuse protection can be conveniently added at any stage in the installation process without requiring additional panel space. It is also desirable to provide an electric control device adaptable for use with either standard cartridge-type fuses or reject-type fuses.
Contactors of the type described in U.S. Pat. No. 3,296,567 issued on Jan. 3, 1967 to John P. Conner and Kurt A. Grunert and assigned to the assignee of the present application include provision for mounting additional contacts, pole units, or interlocks for actuation by the operating mechanism of the contactor. It is desirable to provide a fusible electric control device compatible with such contactors.